Cellulose/polymer mixtures are used to make a variety of products. For example, products made from a cellulose/polymer mixture range from food containers to building components. It is of extreme importance that the consistency, concentration or other physical property be accurately determined.
Cellulose is a complex carbohydrate, i.e., a polysaccharide, that forms the major part of the cell walls of all plants and is practically pure in the fibers of cotton, flax, jute, and ramie. Cellulose is insoluble in water and is rather inert chemically, although it may undergo reactions typical of the alcohols because each glucose unit has three hydroxyl (OH) groups. Paper is an impure cellulose derived from wood pulp, made by removing the lignin by one of several processes.
Polymers are large molecules that contain many repeating units, thus the formatives: poly=many and mer=units. Polymerization is the reaction in which small molecules react to form large molecules or polymers. Polymers have a wide use as plastics, finishes, and fibers. For a molecule, called a monomer, to form a polymer, it must have at least two reactive sites; that is, it must be difunctional. An example of a difunctional molecule is hydroxy acid. The hydroxyl (OH) group of one hydroxy acid monomer reacts with the carboxyl group (COOH) of another hydroxy acid monomer to form an ester (a dimer). The ester dimer is also difunctional and may react further to form a polyester, with multiple units in the polymer chain. It is appreciated by those skilled in the art that polymers may be formed in many ways to include many types of molecules. Typically, polymers are considered to have useful mechanical properties if they are of sufficiently high molecular weight.
In conventional practice, the polymer content of products made from cellulose/polymer mixtures was typically determined after the product was made or formed. Often, the polymer content of the final product was found to be unacceptable. Thus, the unacceptable products were rejected and ultimately sold for scrap, given away or otherwise disposed of.
In the pulp and paper processing industry, conventional testing and controlling devices do not provide for determining the polymer of a cellulose/polymer blend or mixture. The determination of the polymer content of a cellulose/polymer mixture in the pulp and paper processing industry has been, and continues to be, a significant problem. Determining the polymer content is typically inexact, time consuming and potentially hazardous.
Also, determining the polymer content of cellulose/polymer mixtures is subject to many variables. Variables which effect an accurate determination of the polymer content in such mixtures include temperature, reagent stability, moisture content, accurate chemical concentrations, sensitivity to physical parameters and the like. Achieving and maintaining a desired polymer content with respect to a process mixture of cellulose/polymer material is critical to manufacturing using such material. A preliminary determination of the polymer content is of critical importance since the resultant product would be defective with an incorrect polymer content.
Typically, the polymer content of cellulose/polymer mixtures can be determined using differential scanning calorimetry ("DSC"), gravimetric methods, and other analytical methods. The prior used methods have problems which must be overcome for their effective use. For example, with either differential scanning calorimetry or gravimetric methods, the temperature of the test is critical. Also in such prior known methods, the sample of cellulose/polymer mixture must have a weight which is precisely known. Still further, the prior known methods typically require a sample which is essentially free of all moisture. But still further, the use of differential scanning calorimetry or gravimetric methods typically takes in excess of thirty (30) minutes to determine the polymer content of a cellulose/polymer slurry sample causing considerable time delay.
Also of primary importance, some methods require the use of hazardous or corrosive materials. For example, the gravimetric method for determining polymer content of a cellulose/polymer mixture requires the use of cupriethylenediamine. The cupriethylenediamine used in the gravimetric method for determining polymer content is required to dissolve cellulose material. Cupriethylenediamine is hazardous in that it is a corrosive material which can cause burns and blindness upon contact. Yet still further, reagent stability causes additional concentration problems in trying to measure the polymer of a mixture.
It is, therefore, a feature of the present invention to provide a method and apparatus for evaluating a desired polymer of a cellulose/polymer mixture which is free from all the prior discussed problems associated with other methods and apparatus.
A feature of the present invention is to provide a method and apparatus for determining the polymer content in a mixture of polymer and cellulose.
Another feature of the present invention is to provide a method and apparatus that requires only a moist sample to determine the polymer content in a polymer/cellulose mixture.
Yet another feature of the present invention is to provide a method and apparatus which determines the polymer content of a polymer/cellulose mixture prior to the mixture being sent to the processor, paper-making machine or the like.
Still another feature of the present invention is to provide a method and apparatus for determining the polymer content of a polymer/cellulose mixture which avoids the use of hazardous chemicals which increases the probability of damage to property or harm to persons using prior known techniques.
Another feature of the present invention is to provide a method and apparatus for determining the polymer content of a cellulose/polymer mixture which is not sensitive to temperature or moisture as are other conventional methods.
A further feature of the present invention is to provide a method and apparatus for determining the polymer content of a cellulose/polymer mixture which is not sensitive to reagent stability or chemical concentrations as are other conventional methods.
Still another feature of the present invention is to provide a method and apparatus for determining the polymer content of a mixture before the mixture is used to create the end product, and thus, all potentially rejected material can be reused and converted into prime product.
Still another feature of the present invention is to provide a method and apparatus for determining the cellulose/polymer mixture which is exceedingly fast to implement and which decreases or totally eliminates all off quality product.
Additional features and advantages of the invention will be set forth in part in the description which follows, and in part will become apparent from the description, or may be learned by practice of the invention. The features and advantages of the invention may be realized by means of the combinations and steps particularly pointed out in the appended claims.